1. Field of the Invention
This invention relates to a process for improving an adhesive property of an adhering surface of an unsaturated polyester resin, and a sheet used for the process.
More particularly, this invention relates to a process for improving an adhesive property of the adhering surface of molded articles such as a bath tub, a digestor chamber, a gas pipe, a hull, a water service pipe or the like which is prepared from an unsaturated polyester resin, and a sheet used for the process.
2. Description of the Prior Art
Molded articles prepared from fiberglass reinforced plastics such as an unsaturated polyester resin have the following defects:
(1) The molded article has a low adhesiveness on its adhering portion because a sliding surface is formed when an unsaturated polyester resin used for fiber-glass reinforced plastics is left for hardening.
(2) Hardness of the adhering surface of the molded article is considerably high.
In order to increase an adhesive property of an unsaturated polyester resin, there have been proposed a sandblasting or a rotary file for improving an adhesion each of the adhering surface of the desired article or of the connected portions of the two pipes. In the sandblasting, a blast of air or stream laden with sand is applied under strong injection pressure upon the adhering or connecting portions where strong adhesivness are required so as to form a irregular or rugged adhering surface.
In the conventional sandblasting, however, dust containing resinous powder is spread around to injure a worker's health. In addition, the sandblasting device becomes complicated and large, its handling is troublesome, and its productivity is low.
The file polishing has the defects that the polishing is easily varied, it is difficult to carry out production control, resinous powder is spread as in the sandblasting to injure a worker's health, and its productivity is low as well.
The present inventor has carried out the study of eliminating the foregoing disadvantages, and has succeeded in providing a process for improving an adhesive property of the adhering surface of molded articles prepared from an unsaturated polyester resin whereby the unsaturated polyester resin is adhered with a piece of cloth in order to form a strong adhering surface without spreading the detrimental resinous powder.